1. Technical Field
The disclosure relates to projection image display apparatuses.
2. Description of the Related Art
A single-plate projector adopting DMD (digital mirror device) selects a color of light entering DMD timewise by a rotary color wheel to display color images, as described in PTL1. This can be achieved with a relatively compact configuration. However, only one color of light from a light source can always be used, and thus a light utilization efficiency cannot be increased. Accordingly, enhanced light-collecting efficiency has been demanded.
To increase the light-collecting efficiency, the light-collecting F-number on the system side is preferably small. When DMD is used as an image display element, the OFF light is significantly out of entrance pupil of a projection lens, and thus it does not cause any problem. However, light reflected on an untilted portion other than a micromirror of DMD (e.g., light reflected on a front glass of DMD) enters at a position adjacent to the ON light. When part of this beam, scattered light, or diffracted light enters a portion where the ON light enters, i.e., an entrance pupil of the projection lens, unnecessary light invades a projected image.
In this case, a beam portion that may become the above unnecessary light is blocked typically by a metal plate. However, this will also block a portion that is originally effective as projected light, resulting in decreasing the light-collecting efficiency